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Improving PPP–RTK in urban environment by tightly coupled integration of GNSS and INS

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Abstract

In order to fully exploit the advantages of both precise point positioning (PPP) and real-time kinematic (RTK), a PPP–RTK method has been proposed to achieve centimeter-level positioning by applying the rapid integer ambiguity resolution, which is now widely implemented in some commercial systems such as Trimble RTX-Fast and NavCom StarFire. Nevertheless, the performance of PPP–RTK faces with restrictions under the circumstance of urban environments due to intermittent signal interruptions and unfavorable tracking geometry. Presently, it is increasingly prevalent that the inertial navigation system (INS) is integrated with global navigation satellite system (GNSS) to serve for enhancing the positioning performance. In this contribution, a tightly coupled PPP–RTK/INS integration model is developed, aiming to provide continuous and precise positioning service under the complex urban environments. In the proposed model, the precise atmospheric corrections derived from the multi-GNSS PPP fixed solutions of reference stations are disseminated to users to enable the rapid ambiguity resolution in PPP–RTK/INS. Furthermore, the high-accuracy position information offered by INS is also used to enhance the performance of ambiguity fixing. Experiments in different scenarios of urban roads and overpasses were designed to verify the effectiveness of the proposed method. Results indicate that the solution availability, fixing percentage and positioning accuracy can be significantly improved by PPP–RTK/INS integration. The horizontal positioning accuracy of the tightly coupled PPP–RTK/INS is 1–2 cm in a semi-urban environment and 5–6 cm in a real urban environment with a fixing percentage of 90.7% and 81.2%, respectively. Moreover, INS information also shows capability of bridging the gaps in GNSS data, which enables continuous positioning and fast ambiguity re-fixing under the GNSS-challenged environments. A fast ambiguity recovery within 1–5 s could be achieved for PPP–RTK/INS after outages lasting up to 30 s, while 8–18 s is required for PPP–RTK.

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Data availability

The datasets collected in the road vehicular test campaign are available on the Web site of international GNSS Monitoring and Assessment System (iGMAS) Innovation Center (http://igmas.users.sgg.whu.edu.cn/group/tool/10).

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Acknowledgements

This work was supported by the National Natural Science Foundation of China (Grant 41774030, Grant 41974027 and Grant 41974029), the Hubei Province Natural Science Foundation of China (Grant 2018CFA081 and Grant 2020CFA002), the Technology Innovation Special Project (Major Program) of Hubei Province of China (Grant No. 2019AAA043), the frontier project of basic application from Wuhan Science and Technology Bureau (Grant 2019010701011395) and the Sino-German Mobility Programme (Grant No. M-0054). The numerical calculations in this paper have been done on the supercomputing system in the Supercomputing Center of Wuhan University.

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  1. School of Geodesy and Geomatics, Wuhan University, 129 Luoyu Road, Wuhan, 430079, Hubei, China

    **n Li, **ngxing Li, Jiaxin Huang, Zhiheng Shen, Bo Wang, Yongqiang Yuan & Keke Zhang

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  1. **n Li
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Contributions

X.L. and XX.L. provided the initial idea and designed the experiments for this study; X.L., XX.L., J.H. and H.S. analyzed the data and wrote the manuscript; and B.W., Q.Y. and K.Z. helped with the writing. All authors reviewed the manuscript.

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Correspondence to **ngxing Li.

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Li, X., Li, X., Huang, J. et al. Improving PPP–RTK in urban environment by tightly coupled integration of GNSS and INS. J Geod 95, 132 (2021). https://doi.org/10.1007/s00190-021-01578-6

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